The present invention relates to a mattress for bedding, and more particularly to a mattress for bedding with threads installed therein and having air tubes containing a foamed body in order to maintain the cushion and the shape of the mattress and to improve its durability and to a method and an apparatus for manufacturing the mattress.
A conventional mattress for bedding is a type of mattress with a plurality of coil springs disposed therein and configured to maintain the cushion and shape of the mattress by means of elastic force and elastic restoring force by the plurality of coil springs.
However, such a mattress that has coil springs therein is subject to severe vibrations as an impact applied to a portion of the mattress is transferred to the surroundings of that portion, and a user cannot arbitrarily adjust a degree of cushion of the mattress in accordance with his body since the elastic force of the coil springs is predetermined upon their manufacture. Further, since the elastic force and elastic restoring force of the coil springs are lowered and noise is generated when the coil springs are used for a long period, it is difficult to maintain the cushion and shape of the mattress and in turn the life of the mattress is shortened.
In order to make up for the drawbacks in the coil springs, an air mattress using air was developed previously. That is, the air mattress is configured so that the inner portion of the air mattress is divided into a plurality of partitions by bonding both ends of a respective I-beam to upper and lower inner surfaces of the air mattress and air is injected into each partition. The air mattress is adapted to maintain its cushion and shape by air pressure that is injected into each partition and to arbitrarily set the degree of cushion in conformity to a user's body by adjusting the air pressure.
However, since the air mattress with I-beams installed therein has a plurality of partitions divided widthwise or lengthwise of the mattress, air is moved within the same partition when pressure is applied to a certain portion. Therefore, since a portion to which pressure is applied is recessed due to the depression of the air mattress and the other portions to which pressure is not applied relatively expand and convexly protrude, there is a drawback that the air mattress has on the whole a level of irregularity.
Moreover, if the expansion and contraction of the air mattress are repeated as it is repeatedly used, stress is concentrated on the inner surfaces of the mattress and on both ends of the I-beams attached thereto, and thus, the bonded portions of the I-beams are detached, thereby deteriorating the function of cushion and the shape maintenance, resulting in a useless mattress.
The applicant proposed an air mattress using threads in Korean Patent No. 226611 in consideration of the problems occurred in a mattress using coil springs and an air mattress using I-beams as described above.
That is, the air mattress is configured so that the inner top and bottom surfaces having gastight property (gas impermeability) and liquid-tight property (liquid impermeability) are densely connected by threads, for example, with the density of three or more strands per one square centimeter and air is injected into the air mattress. The air mattress is adapted to maintain its shape with the expansion of the air mattress by the length of the threads.
If the inner top and bottom surfaces are densely connected by a number of threads as described above, even though pressure is applied to a certain portion of the air mattress, only the portion to which the pressure is applied is recessed and the other portions are prevented from further expanding by the length of the threads so that the other portions do not convexly protrude to maintain the shape of the air mattress and merely inner air pressure is slightly increased. Thus, the air mattress can be prevented from having on the whole a level of irregularity.
Further, since air pressure within the air mattress acts uniformly on the whole, stress affected on the individual thread is reduced and this stress is also dispersed due to the dense connections of the threads. Thus, there is no risk that connected portions of the threads are detached and so on, which results in the improvement of durability.
Although such an air mattress using threads described above is excellent, there is a further need for an air mattress that can maintain the cushion and shape of the mattress even when the air leakage occurs.